Since the ozone gas has a high oxidation reactivity, it is heavily used in a field of manufacturing a semiconductor device. The ozone gas forms an insulating oxide film of a wafer, for example, so that it is used for an ozone bleaching of a pulp and an ozone sterilization, for example.
Patent Document 1 describes a conventional technique for enhancing an ozone generation volume density η (=Y/V), for example. Herein, Y indicates an ozone generation amount (=high concentration×gas flow rate) and V indicates a volume of an ozone gas generation apparatus.
In the technique according to Patent Document 1, a discharge gap length in a discharge space in which a dielectric-barrier discharge is generated is shortened from approximately 1 mm to 0.4 mm or less, so that the ozone concentration increases from 100 g/m3 to 200 g/m2 or more, and a high concentration ozone gas can be thereby generated. That is to say, the technique according to Patent Document 1 increases more than double the ozone generation volume density η. Today, a dielectric-barrier discharge is generated in a short gap length of 0.1 mm or less, so that a high concentration ozone of approximately 300 g/m3 can be generated with the same gas flow rate.
In addition to the above configuration, Patent Documents 2 and 3, for example, describe a conventional technique indicative of an ozone generator made by laminating a discharge cell in which a super-thin water-cooled electrode is used.
In the technique of Patent Documents 2 and 3, an electrode thickness is thinned, and a configuration of a gas piping and a cooling water piping is simplified. Thus, in the technique according to Patent Documents 2 and 3, the ozone generation volume density is further enhanced compared with the technique according to Patent Document 1.
In a technique according to Patent Document 4, an ozone gas is generated using an oxygen gas including nitrogen as a raw material gas.
In the technique according to Patent Document 4, a small amount of NO2 gas generated from a nitrogen gas and an oxygen gas mutually and chemically reacts with a discharge light in an dielectric barrier discharge field. Accordingly, an oxygen molecule can be effectively dissociated, and as a result, a high concentration ozone gas is generated.
Patent Document 5 describes a technique of generating a high concentration ozone gas from a high purity oxygen gas alone.
In the technique according to Patent Document 5, the high concentration ozone gas can be generated from the high purity oxygen gas alone using a mutual chemical reaction between a dielectric barrier discharge light and a photocatalyst.
As described above, the technique of generating the high concentration ozone gas is conventionally studied and developed.